The present invention relates generally to fiber-reinforced molding of parts and more particularly to spray equipment for spray-applying fiber-reinforced heat-curable resins containing high ceramic fiber loadings.
In the manufacture of a wide variety of fibrous-reinforced parts (e.g., FRP or fiber glass reinforced parts), it would be desirable to spray apply a unsaturated resin (catalyzed, heat-curable, unsaturated polyester resin) which would contain a high loading (e.g., say, 55% to 75% by weight) of reinforcing fiber (e.g., ceramic fiber like wollastinite fibers of 0.0017 to 0.0059 mm in average particle diameter with aspect ratios of from about 5 to 17). Unfortunately, conventional spray equipment will not properly spray such resins with such high fiber loadings. The spray equipment, especially the spray guns, become plugged easily by the ceramic fibers which makes down time of the equipment particularly troublesome at commercial operations. It is troublesome enough to spray conventional catalyzed unsaturated resins because of premature gelation problems, cleaning of the equipment during down time cycles, and the like. To add a high loading of ceramic fiber means that the equipment would have to spray a resin mix having the consistency of oatmeal, and a mix that is quite abrasive due to the ceramic fiber content.
One approach to solving the problem of air void surface defects in FRP parts, as proposed in U.S. Pat. No. 4,568,604 (expressly incorporated herein by reference), involves the spraying of ceramic fiber-loaded resins over a layer of gel coat which covers the mold. Such a process is limited in its ability to spray high loadings of ceramic fiber (a mixture of calcium silicate and mica). Still, the need for being able to spray resins with high ceramic fiber loadings is underscored by this patent.
The present invention addresses the foregoing problems associated with spray-applying high fiber loaded, thermally-curable, catalyzed resins used in molding of fiber reinforced parts by use of uniquely designed spray equipment.